<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <link type="text/css" rel="stylesheet" href="./css/mycss.css"/>
  <title>Document</title>
</head>
<body>
  <div style="border: solid 10px;"> 
    <div id="div2"></div>  
    <div id="div3"></div>  
  </div>  
    <h1><span>一级</span>标题</h1>
    <div>我是div1</div>
    <div>我是div2</div>


</body>
</html>